Creaking rotor blades

Racer

Senior Member
Joined
Oct 9, 2006
Messages
1,594
Location
Colorado Springs, Colorado USA
Aircraft
Air Command CLT N7512X
I have heard the strangest sound in a set of rotor blades on a friends Xenon Gyro, The blades are I believe 30' long and they appear to be extruded because there are no seams in them anywhere whatsoever.
I am not exactly sure how to describe the sound but I will do my best.
They have a creaking sound in them that sounds much like an old door that the hinges need to be oiled. they also have a faint popping sound and a small rattle sound in them where something inside sounds like it is loose and rolling around. The sound seems to be coming from the center of the blade but hard to be certain of that because sound travels in a hollow tube. One blade seems to be noisier than the other one but they both do it.
It does not take much to make them do it either, tie one blade down and a gentle breeze will move the blades enough to get them creaking like the old door sound that you hear in the movies.
I have inspected the Rotor head and pre rotator 100% and could find no problems whatsoever. I re-torqued the blades to the hub bar according to manufacturer specs and still no improvement. I inspected both rotor blades thoroughly and found no signs of damage on them at all, they looked perfect.
The owner says he has noticed this for a while but it seems to be getting much worse as time goes on.
These blades were bought less than 3 months ago from Xenon and have less than 40 hours on them.
The aircraft has been grounded until we can find out what these strange sounds are. if this is something normal and nothing to worry about fine but this just not seem normal at all to me.

Somebody please help us find out what is going on here because this one has me stumped. :noidea:
 
The blades almost certainly contain internal nose weights; brass or steel rods near the leading edge, bonded to the spar extrusion with an adhesive. Sounds like the glue has let go.

Perhaps there is mechanical fastening in addition to the adhesive so no danger of coming out. But grounding until definitive information is obtained is the right course.

I’m only speculating, I don’t know.
 
You are correct Chuck it does have weights at the outter ends of the blades, one hex head screw and one phillips head screw, not sure if they will come off so we can look inside or not.
 
Here’s an MTO blade section showing internal nose weights.
 

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If the rotor is not tied down and is free to teeter....and then if you gently push up one blade to cause the rotor to teeter, can you hear the same sounds? If so these sounds are probably coming from the teeter assembly.....otherwise what Chuck said.

Or if no sound until you move the cyclic stick....then the sound is probably coming from these controls.....
 
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The blade has to flex a little before it makes the sounds, I listened to the teeter assembly up close as someone else moved the blades and it was quiet, they only make sounda when the blade flexes some.
If these blades are constructed simular to how the MTO blade is that Chuck posted then I can understand how the creaking noises are being created and it should be a non issue and safe to fly.
It is always what you do not know that will take you out, Thank you all for your ideas and inputs.

Racer
 
It's only a non-issue if there are mechanical fasteners to retain the weights, should be easy to tell whether that's the case or not.
 
Hello Racer

You know better that there has to be no lose items in the rotor.
Tell Xenon people and inquire about this and how to check the tip weights.

it can also be lose spar and skin bonding.

Dont fly till you are dam sure that all is OK. But a creaking rotor is spooky.

Regards.
 
Fixing the problem.

Fixing the problem.

Those blades are designed for HELo's Hellocopters and not gyros. I have a set on my KB-2 gyro with a 90hp mac on it and have no problem with them at all. The sounds that U are hearing are the bolts on the struts are not tighten, right and if they are, then it is the ex-trude inside the blade that has cracked. Do a Maginet - Flux on it and it will find the HAIR-LINE CRACK in that blade. :flame: I hope this doesn't happen to your friend until he finds the problem.
 
...If these blades are constructed simular to how the MTO blade is that Chuck posted then I can understand how the creaking noises are being created and it should be a non issue and safe to fly...

Todd, you've impressed me with your safety instincts in the past, but I can't follow you on this one. If the noseweights are cracked and moving around, I can imagine some pretty bad outcomes.
 
My tip weights in my Helicycle blades are designed to be just bolted in. But, they fit tightly into a channel milled out of the spar. I went ahead and bonded them in with epoxy as well. Stan
 
Heres a though, if the extrusion some how had a void in it during pushing at some point and has broken away from some other point, them it might make a sound as it expands and contracts when flexed? I would try to get a good look inside if possible! Blade should not make strange sounds!
I am in no way trying to bash these blades,but they are made by humans and are prone to human failures as ALL manufactures are!
 
I've

I've

flown quite a few hours in a Xenon and I have heard the blades pop sort of during a pre-flight, not every pre-flight, but on a percentage of them. I've looked and looked and I too could not ascertain the source of the noise. It was not a creaking sound but more of a pop, kind of like when I was a kid and there would be a wind and something metal on the flag rope slapped agains the flagpole. Not a loud noise but it was there.
 
As one of the first Xenon owners in America, and a host of the owners site, we have gotten this question before ... because it seems everyone hears some kind of noise from the aircopter rotors.

I have narrowed down the reported sounds to two possible causes.

The first sound I experienced is kind of "ping" ... as if you tapped a telephone support cable with a screwdriver. I get that every once in a while when I move the rotor blade up or down to inspect it. It almost sounds like a temperature shift of the aluminum. I never get this "ping" when rotating or flying.

The second sound is a "clunk". That sound was positively identified as the Bendix gear popping up and hitting the rotor ring gear momentarily. That can happen if your belt tension is a little too tight and you fly in cold weather. The pre-rotator can grab momentarily causing the Bendix gear to pop up. I have found that you need to adjust the belt two times a year to keep it looser in the winter to compensate for the cold-weather contraction of the belt.

I talked to Mark @ Meadow Lake and his seems to be yet a third noise that I have yet to encounter.
 
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Those blades are designed for HELo's Hellocopters and not gyros. I have a set on my KB-2 gyro with a 90hp mac on it and have no problem with them at all. The sounds that U are hearing are the bolts on the struts are not tighten, right and if they are, then it is the ex-trude inside the blade that has cracked. Do a Maginet - Flux on it and it will find the HAIR-LINE CRACK in that blade. :flame: I hope this doesn't happen to your friend until he finds the problem.

I don't think you can Magnaflux an aluminum blade.
 
This sound is a loud creak when you move the blade up and down and it does it 100% of the time. I could closely duplicate this sound by opening and closing a squeaky door on an old Chevy truck.
If these blades have an internal nose weight bar then the two metal surfaces slipping against other under friction could certainly cause this creaking sound.
The ping sound that others are talking about has come from these blades as well but that only happens every now and then, we cannot make them do that ping noise on command like we can with the creaking sound.
There have been calls and E-Mails sent to the manufacturer but have not heard back from them as of yet, hopefully will get some sound information from them soon but until we know for sure what exactly is going on with these blades the gyro will just be patiently sitting and waiting in the hanger.

Thanks everyone for your inputs on this mystery, I am sure we will have the answers in the near future.
 
You are wrong.

You are wrong.

This sound is a loud creak when you move the blade up and down and it does it 100% of the time. I could closely duplicate this sound by opening and closing a squeaky door on an old Chevy truck.
.

Could easly be a ford but never a chevy.

Graeme.
 
Maybe applying pressure and using a estetoscope can bring out some clue.
The blades seem to have a problem, talking about it is not bashing.
Camera and microphone will help recording images and sounds.
Heron
 
Racer,
Maybe the people at Vortex has run into that problem before and they can tell you what it is. It does make since that if there is a balance rod running it the length of the rotor and it has detached itself along the way, that it would resist moving with the rest of the rotor. I think Heron had a good ideal with the stethoscope like mechanics use to diagnose engine noises.
Good luck, sorry the machine is grounded, that's a bummber
 
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